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A 4-year-old boy walking on the beach with his mother on the Outer Banks was hit by a wave and swept out to sea on Wednesday, officials say.

The child still had not been found as of Friday afternoon.

The boy and his mother were walking on the beach in Kitty Hawk, North Carolina, late Wednesday afternoon when a wave hit the child, the U.S. Coast Guard said in a statement. His mother "lost sight of him in the surf."

The Coast Guard responded about 4 p.m. and searched for the boy by helicopter and by boat. They searched 130 square nautical miles for hours but still couldn't find him. At 8:30 p.m., they suspended their search.

"As parents, this is our worst nightmare, even for those of us who love and have grown up by the ocean," the department said on Facebook. "Please join us in thought and prayer for this family as we mourn with them the loss and give thanks for the well-being of our own children."

Neither the Coast Guard nor the police department gave the child's name.

A family member of the missing boy declined an interview request by WAVY but said they were hoping for closure soon. They were visiting the Outer Banks from New Hampshire. The boy is their only child.